The generation of energy from waves is the conversion of the motion energy of waves at the ocean surface into, for example, electrical energy. To allow utilization of the energy of ocean waves, the kinetic energy can be converted into a linear motion with the aid of the relative deflection of floats. One example is the “sea serpent” (Greek “pelamis”) configuration for wave power converters. These are made up of multiple tubular steel segments movably connected to one another via joints. Hydraulic pumps are mounted at the joints and drive a generator. Another example is so-called point absorbers. These are floating apparatuses having components that move relative to one another as a result of wave motion, for example a floating buoy inside a stationary cylinder. The relative motion of the components is used to operate electromechanical or hydraulic energy converters.
An energy conversion device for converting wave energy is described, for example, in German Patent Application No. DE 10 2009 035 928 A1. This conversion device has at least one coupling element, disposed in a fluid, which is set up to couple to at least one orbital flow motion associated with the wave motion of the fluid. The conversion device further has a guidance device that defines a guided, endlessly circulating orbital motion and/or rotary motion of the at least one coupling element. The guidance device has a drive system at which it converts the circulating motion and/or rotary motion into a torque.
Electroactive polymers (EAPs) are polymers that change shape as a result of the application of an electrical voltage.
Electroactive polymers are therefore used as actuators or sensors. Electroactive polymers also make possible a generator mode, however, in which mechanical elongation energy is converted directly into electrical energy. Energy converters of this kind are referred to as “EAP generators.” Conversion of the elongation energy into electrical energy occurs on a capacitive basis as a result of charge displacement. In the context of energy recovery using EAPs, the EAP generator, encompassing at least one component that encompasses two resilient electrodes between which is disposed a layer of electroactive polymer, is elongated as a result of an externally applied force. When the EAP generator is in the state of maximum elongation, the assemblage is impinged upon by electrical charges below the breakdown field strength. As the externally applied force decreases, the EAP relaxes because of the elastic effect of the polymer. The energy stored in the EAP generator increases in this phase. This operation represents the actual conversion of mechanical energy into electrical energy. As soon as the EAP generator is completely relaxed, the assemblage is discharged, with the result that the EAP returns to its original length. The energy recovery cycle can begin again.
For EAP generators, multiple plies, each encompassing two electrodes between which a layer of an electroactive polymer is disposed, can be combined into an EAP stack. For the present invention, however, the term “EAP stack” is also understood as embodiments that have only one ply made up of two electrodes having between them a layer of electroactive polymer. “EAP stacks” for purposes of the present invention are therefore stacks that have at least one ply encompassing two preferably flexible electrodes and a layer of electroactive polymer disposed between the two electrodes. For EAP generators, the EAP stack or multiple EAP stacks are disposed between two force-transferring surfaces disposed parallel to one another, preferably in such a way that the plies of the EAP stack are disposed parallel to the force-transferring surfaces. As soon as a force is exerted via these surfaces onto an EAP stack, the stack becomes compressed in a vertical direction, i.e., in the direction perpendicular to the force-transferring surface, but at the same time it elongates in a horizontal direction, i.e., in the plane of the plies of the EAP stack, relative to the EAP plies. The horizontal elongation of an EAP stack is impeded at both of its ends by the frictional forces between the end surfaces of the EAP stack and the force-transferring surfaces. This results in bulging of the EAP stack and, associated therewith, non-optimal energy conversion.